The present invention relates to a cooling device of a heating furnace provided in a thermal analyzer.
A conventional cooling device has a structure, for example, as shown in FIG. 5 and disclosed in Japanese Utility Model registration Application, Laid Open No. 22549/1987. As seen from FIG. 5, this conventional cooling device is constructed such that the entire portion of a heating furnace 59, including a sample replacement opening on a top portion of the furnace, is covered with a Dewar Vessel 57.
For measurements in this type of thermal analyzer, in order to impart to a sample a particular thermal hysteresis or thermal shock (for example, rapid cooling), the sample may be set in the heating furnace held at a particular temperature in a range below room temperature. In such case, according to the conventional structure, since the Dewar Vessel 57 entirely encloses the heating furnace 59, the Dewar Vessel must be removed in order to set a sample in the heating furnace. However, when removing the Dewar Vessel 57 in the prior art structure, atmospheric temperature around the heating furnace 59 rises to room temperature, thereby making it difficult to hold the heating furnace at the particular desired temperature below the room temperature. Consequently, measurements of the above-mentioned mode cannot be actually carried out, this representing a serious drawback in the conventional structure.
Recently, analyzers of the above kind are desirably provided with a robot mechanism, such as an auto-sampler, operable to effect automatic replacement and setting of a sample. In a thermal analyzer provided with a robot mechanism, such as an auto-sampler or auto-manipulator, the robot mechanism has to be operated to remove and return the Dewar Vessel 57 during the replacement and setting of a sample in the conventional structure. However, while a sample which is an object of the replacement and setting operation has normally a weight of less than 1 g, the Dewar Vessel of this type has a far heavier weight normally in the range from 500 g to 1000 g. Accordingly, the robot mechanism is normally constructed and set to handle the small weight of the sample which is the object of the replacement and setting, so that the identical robot mechanism cannot properly effect removal and return of the Dewar Vessel due to the considerable weight difference. Therefore, when providing a robot mechanism functioning as an auto-sampler, an additional robot mechanism is also needed to remove and return the Dewar Vessel 57, in addition to the robot mechanism used for replacement and setting of the sample.
As noted above, in the prior art, since the entirety of the heating furnace is surrounded by the Dewar Vessel, there have been various problems such as the difficulty of sample replacement while controlling the furnace below room temperature, and the necessity of an additional mechanism for removing the Dewar Vessel in addition to the main robot mechanism which is especially designed to handle the sample which is the object of the replacement and setting, and therefore, difficulties in replacing the sample.
The present invention is directed to an improved cooling device of the thermal analyzer, effective to facilitate the sample replacement and to carry out cooling as efficiently as the prior art structure while not utilizing a Dewar Vessel which would have to be displaced during the sample replacement.